Peculiarities of ethane oxidation on V 2O 5/SiO 2 catalysts with different silica structure and morphology

Abstract

Peculiarities of catalytic ethane oxidation with O 2 are studied on a series of V 2O 5/SiO 2 catalysts prepared by impregnation/oxidative calcination. Catalysts differ in structure and morphology of the starting silica. The samples supported on amorphous SiO 2 prepared by different methods ( S BET 330–680 m 2/g) are compared with catalysts supported on SiO 2 with mesoporous MCM-41 structure and silicalite with ZSM-5 structure. FTIR, DTA and ESR techniques are used to monitor the properties of catalysts. Catalytic testing at 450–600 °C demonstrates a drastic difference in the selectivity of the oxidation process on vanadia species stabilized by different types of silica. The catalyst supported on SiO 2 prepared by sol–gel method shows substantial activity in total ethane oxidation, with negligible contribution of oxidative dehydrogenation (ODH). On the other hand, the sample V 2O 5/MCM-41 demonstrates a surprisingly high level of ethene formation and relatively low activity in total oxidation, with selectivity of dehydrogenation reaching ∼50% at 500–600 °C. Only trace amounts of oxygenates are formed in all cases. ESR data demonstrate a substantial difference in dispersion and redox properties of supported active V-phases in catalysts. Thus, peculiarities of the structure and morphology of the pure silica can control the structure and redox properties of the supported vanadium oxide species even in the absence of modifying additives.